set_aspect_ratio · Nanobanana MCP: Risk & Policy

WHAT IT DOES

What set_aspect_ratio does on Nanobanana

AI agents use set_aspect_ratio to create or update resources in Nanobanana — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Nanobanana environment.

WHY IT NEEDS A POLICY

Why set_aspect_ratio needs a policy

The tool modifies session state by changing a parameter (aspect ratio) that controls how subsequent image generation/editing will behave. This is a reversible, non-destructive configuration change—characteristic of Write operations. The blast radius is minimal since it only affects the formatting of images generated within the session and can be changed again at any time.

From the tool's definition Tool description states it "Set[s] the aspect ratio for subsequent image generation and editing in this session." This is a configuration modification that affects future operations but does not retrieve data (not Read), execute arbitrary code (not Execute),…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_aspect_ratio Rate-limited

set_aspect_ratio stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_aspect_ratio": {
      "limits": [
        {
          "counter": "set_aspect_ratio_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Nanobanana, so you can run agents against it safely.

FAQ

Questions about set_aspect_ratio

What does the set_aspect_ratio tool do? +

Set the aspect ratio for subsequent image generation and editing in this session. Must be called before generating/editing images if a specific ratio is desired. It is categorised as a Write tool in the Nanobanana MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_aspect_ratio? +

Register the Nanobanana MCP server in PolicyLayer and add a rule for set_aspect_ratio: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Nanobanana. Nothing to install.

What risk level is set_aspect_ratio? +

set_aspect_ratio is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_aspect_ratio? +

Yes. Add a rate_limit block to the set_aspect_ratio rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block set_aspect_ratio completely? +

Set action: deny in the PolicyLayer policy for set_aspect_ratio. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides set_aspect_ratio? +

set_aspect_ratio is provided by the Nanobanana MCP server (@ycse/nanobanana-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.